Presence data describes one or more characteristics regarding a user's current interaction with a presence-based system, such as an instant messaging system. For instance, the presence-based system can communicate status-related presence data to a user's contacts. This type of presence data may inform the contacts that the user is currently online, away, busy, and so forth. The presence-based messaging system can also convey personal data to the user's contacts. The personal data may reveal a personal textual message associated with the user, a display name, and so forth. Instant messaging systems can convey yet other types of presence data. In each case, the presence data generally serves the operational role of facilitating communication among users of the system, e.g., by giving users insight as to what is happening among communication participants.
Message data describes the actual content of messages being exchanged among communication participants. In the case of one type of presence-based system, the message data may include mainly textual content.